T3P3 Kossel Mini Kit Release 3

Assembly Instructions

Chapter 17 - Test Printing

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1701 Install and Run Slic3r

Slic3r is software used to produce G-code print files from the STL files produced by CAD programs.You should download the latest stable version of Slic3r from http://slic3r.org/download/. If you are running Linux you should also read the installation instructions on the Github Slic3r page linked to from the Slic3 download page. The 32 and 64-bit Windows versions of Slic3r current at the time of writing are also stored on the SD card supplied with your kit.

These installation and start-up instructions are written for the Windows version. Unzip the appropriate version of Slic3r (32 or 64-bit) to a folder of your choice. There is no installer script, and the GUI version of Slic3r is run by clicking on slic3r.exe.

When you run it for the first time, the Configuration Wizard will open.

You should cancel this and instead import the MKR3-Slic3r_config_bundle.ini  configuration file from wherever you backed up the uSD card on your hard drive,  using File/Load Config Bundle.

After loading the config bundle, Slic3r will open in Simple mode, but you need to change to  Expert mode to gain access to all Slic3r’s features, so  do so right away. Choose File>Preferences and select Expert in the drop-down box.

You will now have to restart Slic3r and then import the MKR3-Slic3r_config_bundle.ini file again. If you are new to 3D printing, this would be a good point to review the first four sections of the Slic3r online manual for an overview of the main features and settings.

1702 Prepare Printbed

NOTE: Some of the pictures below show a mirror glass printbed. This is unsuitable for use with the DC42 IR probe and we now supply a plain glass printbed, and also a sheet of black paper to place under it. Early kits we supplied with black paper uncut - if so you should trim the paper to size as described in Chapter 15 Section 1505 and fit it under the glass.

The glass printbed needs to be prepared to help the first layer of molten PLA to stick well. The most common preparation methods are to spray it with hairspray, cover it with Scotch Blue painters’ tape or apply a thin layer of a PVA-based adhesive like a Pritt or UHU stick. We have tried all 3 and concluded that a Pritt adhesive stick works as well as Scotch blue tape and is much easier to apply, so we have provided a tube of Pritt stick in the kit and suggest you start with it. Some of our customers have had better results with blue tape lightly wiped with alcohol (methylated spirits or isopropyl) before printing.  You may wish to try these options if you have adhesion problems with the Pritt stick.

You may find it easier to remove the glass printbed from the printer to prepare it. Apply the glue stick thinly and evenly onto the cold glass plate.


Try to keep the application thin and even. Then clip the glass printbed to the heatbed again.


2003 Print Test Object

The sample filament we provide has an effective diameter of 1.75 mm +/- 0.05mm. The default Slic3r settings assume 1.75 mm which is close enough for now, but when you start buying your own filament, you should check the diameter with digital calipers. Ensure the filament is measured directly across, straightened out of its natural curve. Make at least 2 measurements at 90 degrees and take the average. Enter the measured diameter in Slic3r.

Open Slic3r and select the Plater tab.

Locate the 30mm-hollow-box.stl  file in the Test_objects folder (in Slic3r folder for early kits) which was on the uSD card supplied with the kit. Drag and drop it onto the grid of the Plater tab in Slic3r.

Before exporting it as Gcode, double-check that Print, Filament and Print Settings are all set to MKR3  Draft. This is a good habit to get into once you build up a selection of different saved settings.

Warning: Some users have found that the PVA adhesive layer on the print-bed can affect the accuracy of auto-calibration, which is run by default at the beginning of every print. If you are satisfied with the accuracy of calibration achieved in Section 16, you may like to try printing without initial probing. To turn off autocalibration at the beginning of every print, go to the Printer Settings Tab, click on Custom G-code and comment out the G32 command in the Start G-code window with a ;  (semicolon)

Click on Export G-code and the program will ask you where to save it and under what filename. The default is the same filename as the .stl file, in the same folder - in this case 30mm-hollow-box.gcode. Later on you may want to add descriptors to the filename such as Black-175-200C-30mm-hollow-box.gcode to identify filament colour, diameter and print temperature, as well as the object.

Open the G-code Files page of the web interface, connect to the printer, power it on and set the heated bed to 65C and the hot end to 200C. Click on Load, navigate to 30mm-hollow-box.gcode and select it.

Once the temperatures reach their set-points, click on the Print button and confirm that you want to print the selected file. The printer will Home itself, run autocalibration using the Z-probe, and may then pause briefly to confirm the hot-end is up to temperature.

[The following pictures still show a print bed covered in blue painter’s tape - please ignore this].

You should always watch the beginning of the print to confirm that all goes well. This is particularly important when starting to print with a new and untried filament which may behave differently. Occasionally the border around the print may become detached and get in the way of the print.

Once the print is well under way you can leave it and get on with other things.


When the print finishes, the printer will home itself.

Carefully remove the print from the printbed. The 30mm hollow box test print should come off quite easily, but for large flat objects you may need to use a knife blade or similar to lift one corner. A sharp chisel, used very carefully, can be ideal.

If you have vernier calipers you should now measure the 30mm box and confirm that it is close to 30mm in all 3 dimensions. With autocalibration it should be accurate to within + 0.2mm. Fine-tuning to achieve even better accuracy is beyond the scope of this manual, but help with this is available on the web.You can now go on to slice, print and measure the other test object, 5mm_Calibration_Steps.stl.

If all has gone well so far, it only remains to tidy up the printer, fit the spoolholder and start printing other objects!


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